This article describes the experience in Spain of a specific collaboration between university teachers and school counselors, which used case-based approaches in a teacher training program. The collaboration ran for four years and involved 300 graduate students, two university teachers, and six school counselors. Three basic features enabled this collaboration: a) horizontal relationships, b) a spirit of mutual help and confidence, and c) autonomy. The outcome of the experience can be evaluated in terms of both the case-based teaching process itself and its impact on student learning and the professional development of teachers and counselors involved.